The page length is automatically controlled by the amount of content you want in your service. To reduce the number of pages delete items (click the trash can icon when an element is highlighted, see image below), conversely if you add photos, songs, hymns or other items pages will be added by the system.
The site is designed to create beautiful booklets for printing. This means that the number of pages increases dependent on the number of sheets as well as pages (think about what happens when you fold a piece of paper to make a booklet ) in short this means you page length goes up in 4s : 4, 8, 12, 16 etc